Electromechanical linear actuators are well known and have many and diverse uses. For example, in the treatment of potable waters, linear motion valve actuators often serve to regulate the feedrate of a gas feeder, typically chlorine, to the potable waters for disinfection thereof.
In the regulation or control of a linear motion valve feeding chlorine gas to potable waters, for example, a conventional analyzer, disposed externally to the present actuator, generates signals indicative of the quantity of residual chlorine in the water. A controller, maintained at a desired set-point of residual chlorine, receives the analyzer signals and compares the analyzed residual chlorine in the treated water with a desired residual chlorine preset into the controller. The controller generates A.C. signals in response to the comparison; these signals are fed to a reversible A.C. motor associated with the present actuator mechanism. The motor positions an output rack which functions to control the chlorine feed valve. Thus, if a higher residual is desired, the controller will cause the motor to run in a forward direction to open, or further open the linear motion valve, and conversely when the residual is to be reduced.
It is desirable in such applications that an accurate indication of valve position be made known to the controller and operator. Further, the manual override means of any automatically controlled electromechanical linear actuator should be readily accessible to the operator as well as simple to operate.
The present actuator device maintains a valve position indicator, and an output rack indicative of the output of the valve, directly coupled in both automatic and manual operation modes. Mode change, i.e., automatic to manual, or vice versa, may easily be made by the simple expediency of moving a knob. The linear actuating device may be mounted in a gas feeder cabinet, for example, where the knob is readily accessible from a front panel thereof.